Method of calendering sheet material



Deco 112,. El5 c. E. DELL. 23 533 228 METHOD OF CALENDERING SHEETMATERIAL Filed Oct. 12, 1946 FIGJ IN V EN TOR.

Patented Dec. 12, 1950 METHOD OF CALENDERINGSHEET MATERIAL Charles E.Dill, Dover, N.. 1., assignor to Armstrong-Cork Company, Lancaster, 2a.,a corporation of Pennsylvania Application October 12, 1946, S'eriaINo.702,966

7 Claims. 1

This invention relates to a. method of applying a film of lubricant tocalender rolls to prevent. sheet material passing therebetween fromadhering to the rolls, and toapply a film of wax to the. surface of thesheet material.

An object of this invention is to provide a means for preventing asphalttile sheets or other thermoplastic sheets from adhering to the hotcalender roll during the sheet finishing operation. A further object istoproduce a fiooring tile having a surface free from chill marks orsmall breaks. A still further object is to apply a coating of wax to thesurface of the tile at the time it passes through the finishingcalender, thereby eliminating the subsequent waxing operation in themanufacture of flooring tile of this kind.

The use of lubricants to prevent calendered sheets from adhering to thecalender rolls is old in the art of manufacturing sheet material, butthe lubricating oil usually used for this purpose is not satisfactoryfor the manufacturing process here under consideration due to the factthat the binder for the thermoplastic sheet material is compatible withthe lubricating oil. This causes a certain amount of binder to bedissolved in the oil resulting in defective material due to the factthat only a partial amount of the required binder remains in thefinished product.

Attempts have been made to produce asphalt tile by means of coldcalender rolls (below 130 F.). This process prevents the sheets fromadhering to the rolls but the cold roll produces chill marks on thesurface of the tile sheets. These chill marks are actually small cracksor breaks in the surf'aceof the tile and are highly undesirable in thewear surface of hard surface fioor covering. Furthermore, it has beencustomary in the past to apply a'film of wax to the finished materialbefore it is packaged for shipment to the dealer. This requires anotherstep in the process of manufacturing asphalt tile.

By my invention it is possible to make asphalt tile from the, usualthermoplastic mass and pass it through a calender-having a'heated facingroll. This-is: accomplished by spraying a film of wax emulsion on theheated. roll. The binder used in asphalt tile composition is notwatersoluble and, therefore, any small amount of water remaining in thewax emulsion has; no effect upon the binder. Furthermore, the waxemulsion used to. prevent the sheets from adhering to the calender rollremains on the surface of the sheet material and serves as a wax coatingto protect the wear surface of the. flooring material,

In the manufacture of asphalt tile, the ingredients: are thoroughlymixed in an internal mixer, at the completion of which the loosethermoplastic mix is dumped into a sheeting calender, one roll of whichoperates at about 325 F., and the other of which operates at about 180F. This sheeting calender performs the step of initial heatconsolidation of the loose mass into sheet form. A suitable scraper ordoctor blade is, provided to free the sheets from the. hot roll on thisinitial heat consolidating calender. From this initial sheetingcalender, the sheets travel by meanaof a suitable conveyor to asecondcalender known as a finishing, or facing calender, the top roll of whichs maintained at between 180 and 250 F. and the bottom roll of which ismaintained at about F. This finishing or facing calender effects finalheat consolidation of the thermoplastic mass. The temperature at whichthe hot roll on this finishing calender operates is sufficiently high tocause the surface of the sheets to adhere to the roll. The bottom rollor cold roll is operated at a temperature sufficiently low to preventthe sheet from adhering thereto.

To overcome the problem of the sheets adhering to the hot roll, I havearranged a series of sprayer nozzles; suitable for spraying a film ofaqueous wax emulsion to the surface of the roll. In addition to thissprayer device, a wiper is provided to evenly distribute the aqueous waxemulsion in-v a film of uniform thickness throughout: the width of theroll. This lubricated roll serves as. the finishing roll or facing rollin the final calendering operation and the lubricated surface thereofprevents the face of the sheets from adhering to the calender roll.Also, the lubricated roll transfers a film of lubricant to the surfaceof the sheet being calendered. The thermoplastic sheet. material as itpasses through the.v finishing calenderis at a temperature ofapproximately 250 F. Inasmuch as this temperature is substantially abovethe boiling, point of the water in the wax emulsion, the water is boiledofi, leaving a film of wax on the surface of the sheet material.

After this final calendering operation, the sheets pass through a.cooling zone and then a dieing operation which forms'the asphalt tile tothe desired size and shape.

The-accompanying drawing shows a diagrammatic view of an asphalt tilecalender suitable for carrying out the process of my invention. In thisdrawing, 2 is aconventional facing roll or hot roll which is maintainedat a temperature of between 180 F. to 25.0 F. A series of suitable spraynozzles, indicated at it, is provided for applying a. film, of waxemulsion to the surface essential that the wax be disposed uniformly onthe roll, not only to prevent particles from adhering to all areas ofthe roll but to transfer auniform film of wax to the face of thecalendered tile. The cold roll, indicated at 3 in the drawing, isusually maintained at a temperature of approximately 130 F. At this lowtemperature, there is. no tendency for the'sheet material to adhere tothe surface of the roll 3.

At 3 there is shown a belt conveyor suitable for delivering theunfinished sheet material to the calender rolls and "5 indicates a beltconveyor suitable for carrying the finished waxed sheets away from thefinishing calender to the subsequent dieing operation.

In carrying out the process of my invention, the best results have beenobtained by use of the sprayer-wiper combination explained above,although the invention can be carried out in various other ways such asthe use of a wick for applying wax emulsion to the rolls. Also the waxemulsion may be dropped on the roll by gravity instead of by the sprayersystem.

Several of the commercially obtainable wax emulsions have been found tobe satisfactory in carrying out the process of my invention, but I havefound the best results to be obtained with an emulsion of the followingformulation:

2 Pounds Carnauba wax 100 'Iriethanolamine 14 Borax 6 Nhite oleine 14Sufficient water to form an emulsioncontaining 15% solids.

While the above formulation is preferred for carrying out my invention,it will be understood, of course, that other waxes in emulsion form maybe employed satisfactorily,

I have found the best results to be obtained with a wax emulsion havinga solids content of 15%, however, satisfactory results are obtained withsolids content ranging from 12 to 25%. If more than 25% solids arepresent in the emulsion, there is a tendency for the wax to build up onthe roll rather than be transferred from the roll to the surface or hesheet material. Also, if an emulsion containing a greater percentage ofsolids is used, the wiper becomes clogged and does not perform itsproper function in distributing the wax emulsion uniformly across thesurface of the roll. If the emulsion contains less than 12 solids, itdoes not prevent the surface of the sheet material from adhering to thecalender roll, and, furthermore, the wax film remaining on the wearsurface of the tile is not sufficiently heavy to properly protect thetile.

In the manufacture of asphalt tile in accordance with the processoutlined above, the difficulty of the face of the tile sticking tov thehot roll has been eliminated and the finished tile has a substantiallysmooth wear surface free from chill marks and other defects whichusually arise when a cold roll is used as a facing roll for thismaterial. In addition to this advantage, the sheet material has a filmof wax applied to the wear surface thereof at the time it passes throughthe finishing calender. This eliminates the necessity for having aseparate operation to perform this step in the process of manufacturingasphalt tile or similar flooring materials.

While I have described and illustrated certain preferred embodiments ofmy invention, it will be understood that the invention may be otherwiseembodied and practiced within the scope of the following claims.

I claim:

1. In a method of forming a sheet from a thermoplastic mass, the stepscomprising delivering to the nip between a pair of calendering rolls amass of thermoplastic material heated to a temperature above 212 F., atwhich said heated mass is plastic and may be sheeted by calendering, theface-forming roll of said calender being maintained at a temperature atwhich said heated mass would normally adhere under consolidatingpressure in sheet formation, interposing a film of an aqueous waxemulsion between the surface of the face-forming roll and said heatedmass under treatment, said heated mass being nonadherent to saidface-forming roll with said interposed film under consolidating pressurein sheet formation, consolidating said mass into a sheet between saidrolls with said film of aqueous wax emulsion interposed between saidface-forming roll and said heated mass, removing water from said waxemulsion film by the application of heat thereto from said heated massunder consolidation, and removing the formed and wax coated sheet fromsaid calender rolls substantially free of cracks or breaks in the facethereof.

2. A method in accordance with claim 1 in which the aqueous wax emulsionis sprayed on the face-forming roll to form a film thereon and in whicha portion at least of the film is transferred from the face-forming rollto the face of the consolidated sheet during consolidation and sheetformation.

3. A method in accordance with claim 1 in which the aqueous wax emulsioncontains from 12 76 to 25% of solids.

4. A method in accordance with claim 1 in which the face-forming roll ismaintained at a temperature between 180 F. and 250 F.

5. A. method in accordance with claim 4 in which the mass ofthermoplastic material delivered to the nip between the calender rollsis heated to a temperature of about 250 F.

6. A method in accordance with claim 1 in which the aqueous wax emulsioncomprises by weight parts carnauba wax, 14 parts triethanolamine, 6parts borax, 14 parts white oleine, and sufiicient water to form anemulsion containing from 12 to 25% solids.

7. A method in accordance with claim 1 in which the aqueous w x emulsioncontains about 15% solids.

CHARLES E. DILL.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,312,682 Clapp Aug. 12, 19191,590,638 Marquette June 29, 1926 1,698,267 Kirschbraun Jan. 8, 19292,025,375 Cameron et al Dec. 24, 1935 2,177,240 Brumbaugh Oct. 24, 19392,349,326 Wilson May 23, 1944

1. IN A METHOD OF FORMING A SHEET FROM A THERMOPLASTIC MASS, THE STEPSCOMPRISING DELIVERING TO THE NIP BETWEEN A PAIR OF CALENDERING ROLLS AMASS OF THERMOPLASTIC MATERIAL HEATED TO A TEMPERATURE ABOVE 212*F., ATWHICH SAID HEATED MASS IS PLASTIC AND MAY BE SHEETED BY CALENDARING, THEFACE-FORMING ROLL OF SAID CALENDAR BEING MAINTAINED AT A TEMPERATURE ATWHICH SAID HEATED MASS WOULD NORMALLY ADHERE UNDER CONSOLIDATINGPRESSURE IN SHEET FORMATION, INTERPOSING A FILM OF AN AQUEOUS WAXEMULSION BETWEEN THE SURFACE OF THE FACE-FORMING ROLL AND SAID HEATEDMASS UNDER TREATMENT, SAID HEATED MASS BEING NONADHERENT TO SAIDFACE-FORMING ROLL WITH SAID INTERPOSED FILM UNDER CONSOLIDATING PRESSUREIN SHEET FORMATION, CONSOLIDATING SAID MASS INTO A SHEET BETWEEN SAIDROLLS WITH SAID FILM OF AQUEOUS WAX EMULSION INTERPOSED BETWEEN SAIDFACE-FORMING ROLL AND SAID HEATED MASS, REMOVING WATER FROM SAID WAXEMULSION FILM BY THE APPLICATION OF HEAT THERETO FROM SAID HEATED MASSUNDER CONSOLIDATION, AND REMOVING THE FORMED AND WAX COATED SHEET FROMSAID CALENDAR, ROLLS SUBSTANTIALLY FREE OF CRACKS OR BREAKS IN THE FACETHEREOF.